Muni service, slammed by a three-day epidemic of operators calling in sick, returned to a better state of health Thursday, though Municipal Transportation Agency officials weren't ready to pronounce the sickout over.

"All we can confirm is that there's more service on the street today, certainly compared to the last three days," said Paul Rose, an MTA spokesman.

All transit routes and lines - including the beloved cable cars - were back in normal operation in time for the morning commute and running on regular schedules. As Muni riders know, however, even on a normal day, the transit agency often lacks enough operators to run all scheduled service, and buses and trains frequently show up late - or not at all.

Still, Muni customers had a much easier time catching a ride on Thursday than they did the first three days of the week. Rose said just 45 runs out of 600 were canceled during the morning commute. That number was 718 on Monday, 519 on Tuesday and 266 on Wednesday out of 1,200 daily runs.

The number of drivers who called in sick also declined from 700 on Monday, 538 on Tuesday and 290 on Wednesday to 163 on Thursday. That's still higher than the average absentee rate, which ranges between 94 and 112.

"Things are improving and are a lot better," Rose said. "But we're not at complete strength."

When that will occur, and whether the wave of sick calls will return, is difficult to predict. Muni operators, who pilot buses, light-rail trains, historic streetcars and cable cars, are prohibited from striking, as are all city employees.

But for the first three days this week, operators staged an apparent sickout to protest what they consider unfair contract negotiations and an unreasonable tentative contract. Operators represented by Transport Workers Union Local 250-A rejected the contract on Friday with a vote of 1,198 opposed to the deal and just 47 in favor.

The City Charter, amended by voters in 2010 to deal with Muni contracts, calls for a rejected contract to move to arbitration. The arbitrator is unable to rule against the MTA's proposals unless the union can prove that its interests outweigh "the public interest in efficient and reliable transit."

A hearing with the arbitrator, who also helped mediate the rejected contract, is scheduled for Saturday. But city officials say the union has threatened not to attend, and what happens next seems uncertain.

"We really don't know," said Gabriel Zitrin, a spokesman for the city attorney's office. "The mediator/arbitrator has a lot of leeway."